2008 PM2.5 Plan 

## Chapter 3

What is Needed to Demonstrate Attainment?2008 PM2.5 Plan This page intentionally blank.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-1 

## Chapter 3: What is Needed to Demonstrate

Attainment?

3.1 INTRODUCTION

This chapter describes what is needed to dem onstrate that the S an Joaquin Valley will attain the federal air quality standards fo r PM2.5 in accordance with federally mandated timelines. As required by EPA Guidance, computer modeling and supplemental analysis are used to determine the quantit y of emissions reductions needed from

sources within the District to demonstrate at tainment of the standar ds. The scope of the effort faced by the District to establish a plan sufficient to attain the standards is defined by the local challenges and jurisdictional limitations.

3.2 CHALLENGES

Figure 3-1 San Joaquin Valley Topography

The District must overcome difficult physical environment and regulatory challenges to attain the PM2.5 air quality

standards. Natural conditions including climate, weather (meteorology), chemical reactions and physical processes create an atmospheric environment that forms and retains particulates in the Valley. Improving air quality is made more difficult by population growth that

comes with inherent emission increases and jurisdictional

limits that restrict the comprehensiveness of District

efforts. S a n J o a q u i n

Stanislaus

Merced Madera

F resno

Tulare K ings

KernSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-2 3.2.1 Natural Conditions

The topography and climate in the San Joaq uin Valley create ideal conditions for trapping and holding directly emitted PM2.5 within the Va lley and generating additional PM2.5 from precursor emissi ons. PM2.5 emissions and precursors may be retained within the Valley for several days, recircul ating within the Valley and accumulating to unhealthy levels.

The San Joaquin Valley Air Basin (SJVAB) (F igure 3-1) is a continuous inter-mountain valley encompassing nearly 25,000 square miles. On the western edge of the Valley is the Coast Mountain range with peaks reaching 5,020 feet. On the east side of the Valley is the Sierra Nevada range wit h some peaks exceeding 14,000 feet. The Tehachapi Mountains that fo rm the southern boundary of t he Valley include peaks over 6,000 feet and contain mountain passes to the Los Angeles basin and the Mojave Desert. The surrounding mountain ranges hi nder the movement of air and block removal (dispersion) to other areas by mini mizing wind flows into and out of the air basin, causing pollutants and precursors to be retained within the Valley.

The local climate produces extensive seasonal variations in particulate levels through differences in atmospheric conditions that af fect the types of emissions, emission rates, and atmospheric formation of particles fr om precursor emissi ons. Long periods with little or no rainfall during summer months result in desiccation (extreme dryness) of soils along roadways, increasing emissi ons from traffic movement. Limited rainfall during the summer reduces the frequency of events that clear emissions from the local area. Winter brings rainfall, but also creates an atmospheric environment that forms more ammonium nitrate particulates. During winter, some types of cold winter fog events are linked to atmospheric chemistry that forms additional secondary pa rticulates. The cold weather also induces the public to increase residential wood combustion use that adds further emissions to the atmosphere (though Rule 4901, Wood Burning Fireplaces and Wood Burning Heaters, prohibits fireplace us e when the PM2.5 air qual ity is forecast to be unhealthy).

The SJVAB has an "inland Mediterranean" climat e, which is characterized by hot, dry summers and cool, rainy winters. The SJ VAB averages over 260 sunny days per year (District 2003). During summer months, th e SJVAB is influenced almost continuously from a weather pattern referred to as the “Pacific High” which is a semi-permanent subtropical high-pressure belt of ten located off the west coas t of North America. Major storms and region-wide precipitat ion are not typical when this pressure cell is dominant. The descending air in this cell compresses, raising temperatur es and lowering the relative humidity. This belt of high pressu re migrates north and south seasonally. In winter, the influence of the Pacific High is inte rmittent, giving rise to alternate periods of stormy, unsettled weather and periods of stab le, rainless conditions. Due to the influence of these air movement patterns, air pollutants are generally transported from

the north to the south in the summer and in a reverse flow in the winter. Analysis of wind flow shows that during the winter mont hs, the mean flow is through the Valley from the southeast. By mid-spring, coastal bree zes enter the Valley from the northwest,San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-3 which reverses the airflow pattern. In summe r the northwest to southeast airflow is at its strongest. In the fall and winter, average wind speeds range from five to nine miles per hour; however, very light winds occur fr om twenty to forty per cent of the time.

Precipitation in the SJVAB is confined primarily to the wint er months with nearly ninety percent of the annual precipitation in the SJVAB falling betw een the months of November through April. Average annual ra infall for the entire SJVAB is about ten inches on the valley floor. Annual rainfall tota ls vary from north to south, with northern counties experiencing as much as eleven inches of rainfall and southern counties experiencing as little as four inches per year (District 2003). North-south and east-west regional differences exist, with higher rainfall occurring in the northern and eastern parts

of the SJVAB. Historical evaluations have correlated increased annual rainfall to

decreased PM10 concentrations.

3.2.2 Meteorology

Meteorology plays an important role in determining the leve ls of air pollution in the Valley and is a key parameter to underst anding and predicting PM2.5 concentrations. Meteorological data are used to assess the pot ential for air pollution to accumulate in

certain locations. Pertinent meteor ological parameters include wind speed and direction, ambient atmospheric temperature at different elevations above the ground, precipitation and mixing hei ght (the elevation in the atmosphere into which the emissions will freely mix and disperse).

Meteorological patterns affect PM2.5 by dire ctly affecting emissions (e.g. temperature linked evaporation rates), influencing second ary particle formation (aerosol chemistry) and controlling the rate at which pollution dissipates (wind induced dispersion or inversion restricted flow). The valley fl oor is characterized by warm to hot, dry

summers and cooler winters. Winter temperatures in the SJVAB are generally mild, though temperatures will drop below freezing occasionally . Surface temperatures are dependent on elevation, with co lder temperatures on the mountain ridges both east and west of the valley floor. Fall and winter meteorological conditions contribute to

increased PM2.5 formation shi fting from dominance by prim ary particles to secondary particles. Secondary particles formed from gases by atmospheric processes are a major portion of the PM2.5 during colder, wetter periods from mid November through early February. Colder, frequently stagnant conditions occurring in December and January favor formation of ammonium nitrat e, and these months usually experience the highest levels of PM2.5. During the winte r months, the Valley frequently experiences variable winds of less than 10 mph. Low wind speeds, combined with low-lying inversion layers in the winter and increased secondary particle formation, establish a

situation conducive to the formation and accumulation of PM2.5.

Meteorological factors that restrict horizontal and vertical air movement of air masses are important factors in air quality. Horizont al movement spreads the pollutants over a wider geographic area. Winds carry emissions away from the area of emissions,San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-4 dispersing the emissions and keeping concentr ations low. Emissions accumulate if wind speed is zero or stagnates and recirculat es over a small area. Vertical mixing height is reduced when an inversion layer is present. An inversion layer is a layer of air warmer than the layer below i t. Cooler air below the inversion layer cannot rise through the warmer layer. The warmer layer alo ft prevents the usual rising airflow that disperses emissions from the ground. Air contaminants accumulate near the ground as

emissions continue to be released into th is cooler layer near the surface.

3.2.3 Horizontal Mixing (Transport)

Horizontal mixing, or transport, is also important in the dis persal of air pollutants. The greater the velocity of wind in the mixing layer, the greater the amount of mixing (dispersion) and transport of pollu tants. Winds (at ground le vel or at higher altitudes) transport pollutants from other basins into the Valley, within the Valley to areas downwind, and from t he Valley into other regions. Studying transport increases understanding of how pollution from other ar eas may impact the Valley as well as how pollution originating in Valley areas may impact other places within and beyond the Valley. Evaluation with im proved emissions inventories, improved databases on meteorological behavior and atmospheric chemistry, and im proved grid-based photochemical models all contribute to ongoing studies that enhance our understanding of pollutant transport. Futu re District plans will incorporate any significant advances in knowledge regarding transport as it becomes available from ARB and other agencies.

The amount of pollution transported from ot her areas into the Valley varies. PM2.5 originating from other air basins has not been quantified. During winter, the low wind speeds associated with high particulate leve ls generally reflect concentrations formed from local emissions. However, wildfires , Santa Ana winds, and offshore flow introduce particulates and precursors into the Valley at different times during the year. PM2.5 readings in the SJVAB are most severe during the fall and winter periods when wind speed and direction are not conducive to interregional transport. Monitoring and speciation techniques currently available ar e not able to identify the origin of PM2.5

sources with sufficient detail to indicate if the SJVAB is experi encing transport from outside the air basin. Transport of some PM 2.5 precursors has been studied as part of ozone transport evaluation, identifying transpor t of ozone and ozone precursors from and to other air basins surrounding the SJVAB. The transport of ozone was documented during the summer when the hi ghest ozone readings are more likely to occur. This transport includes precursors of ozone and PM2.5; howe ver, the amount of PM2.5 that could be gener ated in the SJVAB from such transport has not been quantified. Pollution from areas outside of the Valley may or may not contribute to high PM2.5 levels within the Valley.

Transport can also move Valley pollution into ot her air basins. PM2.5 going to other air basins from the SJVAB has not been quantified. During the daytime, heated air rises into the mountains and transports ozone and other pollutants up the Sierra Nevada, Tehachapi, and Coastal Mountains. According to the ARB, the Valley’s pollution canSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-5 affect ozone air quality in the broader Sacr amento area, the Great Basin valleys, the mountain counties, the Mojave Desert, and t he north central and south central coasts, depending on meteorological conditions (ARB 2001). ARB assesses transport corridors for ozone but is not required to perform a sim ilar assessment for particulates. Transport of particulates and precursors was evaluated as part of the California Regional Particulate Air Quality Study (CRPAQS) research program. A specific findings document has not been prepared to quantify t he magnitude of transport between the major air districts; however, preliminary findings did identify that th ere may be occasions of some transport of particles and/or prec ursors from the SJVAB to the Bay Area in winter. A more detailed accounting of inter-basin transport between Bay Area, SJVAB and Sacramento Air Basin may be developed as part of final synthesis documents at the completion of the CRPAQS project.

Precursors and directly emi tted particulates originatin g in the SJVAB are also transported within the Valley. Local emission s are thought to be more responsible for the Valley’s worst ozone and particulate ai r quality. Some SJVAB pollution is not transported into other basins, but remains and recirculates into other parts of the Valley. At night during the summer, cooler drai nage winds from the surrounding mountains prevent exit of the air at the southern end of the SJVAB c ausing a recirculation airflow pattern known as the Fresno eddy. The eddy circulates pollutants in a counterclockwise pattern and returns polluted air to urban ar eas where more precursors are added the next day. Throughout the Valley, some of th e pollutants transported to higher altitudes from daytime heating return to the Valley floor at night bec ause of drainage winds from the mountains. During the winter, flow patterns at the Valley floor may become completely stagnant, keeping emissions within a few miles (or tens of miles) of the originating sources for several days.

3.2.4 Vertical Mixing and Inversion Layers

In general, the air at ground level is warmed by sunlight and activity, causing it to rise and carry emissions aloft. This rising air pa ttern mixes the fresh emissions with air at higher elevations, dispersing the emissions and reducing the concentration of directly emitted PM2.5 and precursors. However, in the San Joaquin Valley a temperature inversion layer frequently blocks the normal ri sing air dispersion pattern. Temperature

inversions are a reversal of the “norma l” decrease in atmos phere temperature with increasing height above the Eart h’s surface. Inversions reflect conditions in which temperature increases with height (Figure 3-2).

Vertical mixing decreases at the base of the inversion, also known as the mixing height. PM2.5 is trapped below the mixing height, rema ining more concentrat ed than when it is allowed to mix more freely into higher elevat ion air. This contributes to higher PM2.5

concentrations in the SJVAB.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-6 Figure 3-2 Vertical Di spersion, With and Wit hout Temperature Inversion

Strong temperature inversions occur thr oughout the SJVAB in the summer, fall, and winter. Inversions are more persistent (s table) in the SJVAB during the winter months, when inversions occur from 50 to 1,000 feet above the SJVAB floor. The challenge this creates for the Valley is that in the absence of an inversi on layer, emissions will not

accumulate to levels that are harmful to heal th. However, if an inversion layer forms the same level of emissions may create loca lized areas with high PM2.5 concentrations. Predicting the strength, elev ation and duration of the inve rsion is based on regional meteorological models supplemented by a few vertical air profiler sites providing local

data. The District uses this information to prepare daily forecasts of air quality and advises the public when conditions are project ed to cause poor air quality. Additionally, the district manages agricu ltural and prescribed burning and residential wood combustion curtailments to avoid adding smoke emissions. when conditions are

unfavorable.

3.2.5 Fog Effects on PM2.5

Particles that become fog dr oplets by absorbing water vapor are subsequently removed by gravitational settling. Fog episodes caus e a net removal of PM by wet deposition. However, fog also provides an aqueous medium for formation of su lfate particulate. The net effect of a fog epi sode depends on the pre-fog conc entrations of particulate precursors and availability of oxidants that are involved in the chemistry of particle formation, and the durati on of the fog event.



## +/- Sulfate is both produced and re moved by fog. The end result of a fog event may

be either increase or decrease in the monitored levels of PM2.5 sulfate. Sulfate particulate is removed by wet deposition dur ing fog; however, fog droplets provide the(b) without inversion (a) inversionSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-7 aqueous medium for the production of sulfates and the production of additional sulfate particulate by chemical reactions. The fog may over-balance the wet removal and actually increase the amount of sulfate PM2.5 in the at mosphere. Whether sulfate formation in fog exceeds sulfate removal by fog settling will vary from site to site, depending on the duration of event and concentrations of ava ilable reactants to form additional sulfate particulate matter.



## - Nitrate and ammonium are partially remove d by fog. Nitrate and ammonia gases in the atmosphere may be reduced by half through fog wet deposition.



## - Secondary Organic Aerosol (SOA) formation (formation of organic carbon particulate from photochemical oxidation reactions of precursor gases) is reduced by decreased photochemical activity in circumstances where sunlight is reduced by fog or cloud cover. Clouds and fog reduce the photochem ical production of secondary organic aerosols by a factor of two or three from the maximum clear sky conditions because of reduced availability of photons. The therm odynamic interactions between fog droplets

and SOA are unknown.

3.2.6 Urban and Rural Comparison an d Atmospheric Chemistry for PM2.5

The major effects of urban emissions ar e observed in the winter where primary emissions typically contribute mo re to PM2.5 at the urban site s than at the rural sites. In urban areas, directly emitted PM2.5 leve ls are dominated by motor vehicle and tire and brake wear emissions, entrained particu late from roadways, and carbon from

residential wood combustion in winter. Precursors to se condary PM2.5 formed from atmospheric processes are dominated by ur ban emissions of nitr ogen oxides (NOx),

sulfur dioxide SO 2 and VOC; however the reactions of these precursors to form particles are dominated by concentrations of nitric acid (HNO 3 ), a secondary compound formed from atmospheric reactions. Ammonia (NH 3 ) emissions are largest in rural areas.

Total oxidized nitrogen is higher in the ur ban areas. NOx in urban areas is ten times

more abundant than in rural areas. Ammonia is more abundant in Bakersfield than at

the other core sites. SO 2 was also more abundant in the cities than rural areas. Gasphase organic concentrations exhibited strong di urnal fluctuations in the urban areas.

District monitoring sites are not dominated by emissions from a single large facility or group of facilities. No direct link has been found between a specific locally observed source of emission activity and high PM2.5 at a single monitoring site on a consistent basis. The observed PM2.5 levels repres ent aggregated urban emissions with regional contributions. In winter, the urban residential and traffic monitor sites show higher

concentrations than sites near industrial areas.

Ammonium nitrate is the main component of PM2.5 during the winter in the San Joaquin Valley. As supported by mode ling evaluation, ammonium ni trate formation is limited by the availability of nitric acid, formed from urban NOx and hydrocarbo n reactions. The

formation of ammonium nitrate is limited by the availability of atmosphericSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-8 concentrations of nitric acid (HNO 3 ), a secondary compound that forms from emission of NOx interacting with hydrocar bons and OH radicals released from the hydrocarbons by photochemical reactions. Ammonia (NH 3 ) is abundant throughout the Valley and does not act as a limiting precurso r. A large fraction of nitrates were associated with the particulate phase; only 18-25% of nitrate existed in the gas phase as nitric acid.

Independent corroboration of key aspects of ammonia contribution to particulate in the San Joaquin Valley is provided through scientific analysis conducted by other researchers. For example: an article by Battye, et al 1 identifies ammonia from motor vehicle exhaust as a major contributor to particulates during winter months with a reduced role for agricultural sources during this time period. This article has important implications for determining which sources of precursors contribute the most to ammonium nitrate particulate concentrations in the winter.

Secondary organic aerosols (SOA) contribute to a significant fraction of PM2.5. SOA is organic carbon particulate formed in the phot ochemical oxidation of anthropogenic and biogenic VOC precursor gases. Aromatic compounds are belie ved to be efficient SOA producers contributing to this secondary particulate.

Annual PM2.5 is dominated by winter concentrations, and urban sites have more carbon. According to the Desert Research Institute (DRI):

“For most of the sites within the SJ V, 50 – 75% of the annual average PM2.5 concentration could be attributed to a high PM2.5 period occurring from November to January. At non-urban site s, the elevated PM2.5 was driven by secondary NH4NO3. The temper ature, RH [relative humi dity], and stability of the valley boundary layer in winter are all favorable for the formation of NH4NO3

from its NH 3 and NOx, and VOC precursors. El evated OM (organic matter, organic carbon compounds) exacerbates air qual ity mostly at urban sites. This is

consistent with the winter use of wood fuel for hom e heating, as well as with traffic. This distinct spatial distribu tion also reflects the difference between primary and secondary aerosols. ...The urban sites experienced much higher BC (black carbon) concentration than non-urban site s. This suggested that BC particles were closely related to urban s ources such as traffic, RWC [residential wood combustion], and cooking. Multiple spikes of hourly BC were frequently observed especially at urban sites, sugges ting that those BC originated from nearby urban sources. At all urban sites, the morning BC peak was found around 0600 to 0800 PST and the large eveni ng peak around 2000 PST prolonged through the midnight and early morning next day. Non-urban sites did not exhibit any distinct diurnal patterns.” 2

1 Source: “Evaluation and improvement of ammoni a emissions inventories” William Battye, etal, Atmospheric Environment 37 (2003) 3873-3883

2 Source: Initial Data Analysis of Field Program Measurements, DRI Docume nt No. 2497, July 29, 2005 Judith C. Chow, L..W. Antony Chen, Douglas H. Lowenthal, Prakash Doraiswamy, Kihong Park, Steven D. Kohl, Dana L. Trimble, John G. Watson, D ESERT RESEARCH INSTITUTE, Di vision of Atmospheric Sciences, 2215 Raggio Parkway, Reno, NV 89512.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-9 3.2.7 Other Key Findi ngs from Scientific St udies and SJV Evaluations

The CRPAQS research program has provided a wealth of sci entific analysis specifically targeted to answer key questions that inform decision-making for effective reduction of particulate concentrations in the San Joaquin Valley. The findings cover a wide range of technical topics. An extensive list of CRPAQS results documents was included in the

2006 PM10 Plan , Appendix D (CRPAQS Bibliography), available on the District's

website at: http://www.valleyair.org/Air_Q uality_Plans/docs/Appendix_D.pdf

The information developed by CRPAQS may have va lue to other areas of the country,

but in some cases the information discloses how California circumst ances are different. For example, EPA methods assume a str ong relationship between sulfate decrease causing a potential and nitrat e formation increase. That issue was studied for the SJV

and found not to be a concern.

3.2.7.1 Ammonium Nitrate Se nsitivity to Sulfate Levels

According to Kumar and Lurmann:

“Ammonium nitrate levels are sensitiv e to changes in sulfate under ammonia

limited conditions. Sulfate and nitrate co mpete for ammonia when its supply is limited, and the thermody namics indicates that a mmonium preferentially associates with sulfate (forming ammoni um sulfate or amm onium bisulfate)

rather than nitrate under ambi ent conditions. Under ammonia limited conditions, reductions in sulfate may not be an effe ctive means to reduce PM mass because

ammonium sulfate removed fr om the aerosol is replac ed with ammonium nitrate, thereby inhibiting significant reduction in PM mass.

The effects of changes in sulfate levels on ammonium nitrat e in the SJV were investigated using the eight cases for whic h isopleth diagrams were constructed. These were cases with relative high sulfat e levels for the SJV (3 to 4 mg/m3). The effects of 50 and 100 percent reducti on in sulfates on ammonium nitrate

concentrations are listed in Table 3-10. The results indicate ammonium nitrate concentrations are not sensitive to large changes in sulfate levels. The lack of ammonium nitrate sensitivity to sulfate in the SJV is due to the ammonia-rich

conditions and the low amounts of sulfate compared to nitrate.” 3

3 Source: ANALYSIS OF ATMOSPHERIC CHEMISTRY DURING 1995 INTEGRATED MONITORING STUDY, STI-997214-1791-FR , Authors: Naresh Kuma r, Frederick W. Lurmann, Sonoma Technology, Inc., Petaluma, CA; Spyros Pandis, Asif Ansari, Carnegie Mellon University, Pittsburgh, PA, July 1998.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-10 3.2.7.2 Precursor Relationships and Control Sensitivity

The issue of limiting precursors and second ary formation products has been extensively evaluated for the CRPAQS research program.

• Particulate NH 4 NO 3 concentrations are limited by the rate of HNO3 formation, rather than by the availability of NH 3

.

• HNO 3 is formed via both daytime photochemistry and aloft nighttime chemistry.

• Secondary organic aerosol formation from VOC emissions may account for
15% to 25% of the total OC

• Relatively low non-methane organic com pounds (NMOC)/NOx ratios indicate the daytime photochemistry is VOC, sunlight, and background-ozone limited

in winter. This is a nonlinear r egime for the gas-phase chemistry. 4

According to Lurmann et al.: “Comparisons of ammonia and nitric acid concentrations indica te that ammonium nitrate formation is limited by the availability of nitric ac id, rather than ammonia.

Time-resolved aerosol nitrate data at the surface and on a 90-m tower suggest both the daytime and nighttime nitric acid formation pathways are active, and that

entrainment of aerosol nitrate formed al oft at night may explain the spatial homogeneity of nitrate in the San J oaquin Valley. ...This study's analyses suggest that reductions in NOx emissions will be more effective in reducing secondary ammonium nitrate aerosol conc entrations than reductions in ammonia

emissions. Reductions in VOC emissi ons will reduce secondary organic aerosol concentrations and may reduce ammonium nitrate. ...Comparisons of ammonia

and nitric acid concentrations show that ammonia is far more abundant than nitric acid, which indicates that ammonium nitrat e formation is limited by the availability of nitric acid, rather than ammonia....T he results indicate ammonium nitrate formation is ultimately controlled by NOx emission rates and the other species, including VOCs and background ozone, which control the rate of NOx oxidation in winter, rather than by ammonia emissions.” 5

The contributing PM2.5 sources have a variet y of properties. This makes analysis of reductions more difficult consequently complic ates the development of effective control programs. Nitrates and car bon are the two largest comp onents, and their atmospheric behavior is entirely different. Ac cording to McCarthy et al.:

“High concentrations of PM organic carbon (OC) were spatially limited to core urban sites while high concentrations of PM ammonium nitrat e were regionally

4 Source: Presented to: CRPAQS Data Analysis Work shop, Sacramento, CA, March 9-10, 2004, Tasks

6.1 and 6.2: Phase Distributions Ta sks 6.1 and 6.2: Phase Distributions and Secondary Formation During Winter and Secondary Formation During Winter in the San Joaquin Valley in the San Joaquin Valley, Presented by: Fred Lurmann, Siana Alcorn, Manidipa Ghosh, Sonoma Technology, Inc., Petaluma, CA

5 Source: Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley During Winter, Frederick W. Lurmann, Steven G. Brown, Michael C. McCarthy, and Paul T. Roberts, Sonoma Technology, Inc., 1360 Redwood Way, Suite C., Petaluma, CA 94954San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-11 distributed throughout the SJV. Concentrati ons of PM and its precursors were typically lower at the elevated sites su rrounding the SJV than at monitoring sites

located on the SJV floor....At distances more than 50 km from the urban areas, OM [organic matter] concentrations typically declined by a factor of three or

more. Emissions of OM at the urban core ar e either not rapidly transported to the

rural sites or are diluted too much to substantially impact rural sites.

Concentrations of OM at elevated sites were comparable to concentrations at rural sites on the Valley floor....Overall, t hese spatial patterns of OM suggest that the impact of emissions was largel y confined to the local area and OM concentrations were unevenly distributed over the duration of the episode.

The contrast in spatial variability between the ammonium nitrate and OM components of PM2.5 in the SJV winter epi sodes provides information on the spatial extent of the produc tion of ammonium nitrate. PM2.5 OM and ammonium nitrate are both subject to the same meteorological transport conditions, yet

ammonium nitrate concentrations are relatively homogeneous and OM concentrations are much higher in the ur ban source areas. In addition, OM and ammonium nitrate components are expected to have the majority of their mass in a similar size fraction (PM0 .1 to PM1) (Lighty et al ., 2000; Hughes et al., 1999; Bench et al., 2002) and, t herefore, the rates of re moval should be approximately the same. In summary, the likely explanation for t he difference in spatial variability is the spatial di stribution of the emissions or precursors. Primary OM emissions occur predominantly from mob ile sources and wood smoke located in

urban areas. The formation of ammonium ni trate from NOx precursors (Lurmann et al., 2004) must occur throughout t he SJV to account for its spatial homogeneity.

High concentrations of PM organic car bon were spatially limited to core urban sites while high concentrations of PM ammonium nitrate were regionally distributed throughout the SJV. The regi onal homogeneity of ammonium nitrate concentrations coupled with the stagnant win d conditions provides evidence that production of ammonium nitrate occurs at similar rates throughout the valley. In contrast, the OC component of PM indicates that pr oduction rates were much higher in the urban areas than at rural sites.” 6

3.2..8 Population Growth

Increased population, which results in incr eased vehicle activity and more consumer product use, leads to increased pollutant em issions, undermining the progress made by regulations. Table 3-1 shows population esti mates for the eight counties of the SJVAB by county, including projections to 2014. In 2006, 9.9% of California’s population resided in the SJVAB (Califor nia Department of Finance 2005) . Population projections

6 Source: Background and Boundary Conditions for Particulate Matter and Precursors in the San Joaquin Valley in Winter (Technical Memorandum STI-902325-2779-TM), Michael C. McCarthy, Hilary R. Hafner, Steven G. Brown, Fredrick W. Lurmann, Paul T. R oberts, Sonoma Technology, Inc., 1360 Redwood Way, Suite C, Petaluma, CA 94954-1169, July 29, 2005.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-12 suggest that 11% of California’s total populat ion will reside in the San Joaquin Valley in 2020. Between 2005 (the base year for this plan) and 2014, the popul ation of the San Joaquin Valley will grow by 43%. In contra st, the total populati on for the State of California will grow 24% over the same time period.

Table 3-1 SJVAB Po pulation by County

County 2005 2014 Projection % Change,

2005-2014

Fresno 837,459 1,015,838 33

Kern a 580,794 718,656 36

Kings 135,218 167,701 37

Madera 129,728 163,753 42

Merced 224,488 310,961 61

San Joaquin 608,594 844,074 63

Stanislaus 479,203 596,967 36

Tulare 384,650 485,889 41

TOTAL 3,380,134 4,303,839 43

a Valley portion; Kern County has portions located outside of the San Joaquin Valley Air Basin. Source: Developed using Population Trends Repor ts, California Department of Finance (2005).

3.2.9 Jurisdictional Limits and Regulatory Authority

Attainment of air quality standards and the reduction of precursor emissions in the SJVAB require the cooperation of local and/or regional, state, and f ederal governments. At the federal level, the EPA is responsib le for establishing federal motor vehicle emission standards. The EPA is also resp onsible for reducing emissions from locomotives, aircraft, heavy duty vehicles used in interstate commerce, and other sources such as off-road engines that are ei ther preempted from st ate control or best regulated at the national level.

The ARB establishes emission standards for on-road motor vehicles and some off-road

sources. The ARB also establishes fuel specifications and develops consumer product standards for meeting air quality goals in California. Other state agencies such as the Department of Pesticide Regu lation (DPR), California D epartment of Transportation (CalTrans), and the Bureau of Automotive Repair (BAR) also have responsibility for

certain emissions sources.

Districts like the San Joaquin Valley Unified Ai r Pollution Control Dis trict have authority to regulate stationary sources and some area sources of emissions. Districts cooperate with Regional Metropolitan Planning Organization (MPOs ) to develop measures affecting local transportation activity that ar e included in a SIP. In turn, the MPOs coordinate the process to identify and evalua te potential control measures and compileSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-13 local government commitments that will be included in the local or regional air quality plan.

The primary jurisdiction of the District is t herefore limited to just part of the total emissions inventory (Figure 3-3). Based on 2005 inventories developed for this plan,
20% of the total NOx inventor y for the SJVAB is under the prim ary regulatory jurisdiction

of the District.

Figure 3-3 NOx Precursor by Source Type 7
(Based on Annual Emissions Inventories)

Oxides of Nitrogen (NOx)

Mobile

Sources

80% Stationar y
and Area

Sources

20%

Although the responsibility for establishi ng the tailpipe emissions standards for the mobile sources belongs to state and federal gov ernments, additional reductions are

needed to reach attainment. Ther efore, the District is also proposing measures, such as trip reduction, green contracting, and enhanced indirect source review, to provide

additional mobile source emissions reductions for this plan and will continue to use incentive programs to accelerate m obile source emissions reductions.

7 Please note that Mobile Sources includes on-road and off -road sources. For NOx, 67% of the total mobile source
emissions in 2005 come from on-road sources, and 33% of t he total mobile source emissions come from other mobile

sources.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-14 3.3 MODELING

The SJVAPCD PM2.5 SIP Modeling Protocol describes the selection of the general modeling approach, methods of analysis, an d identification of data pertinent to supporting modeling analysis. The prot ocol proposes comprehensive analysis combining the results of evaluations, co rrelated and reconciled to establish by preponderance of results (weight of evi dence) that all nonattainment areas will be adequately addressed. EPA guidance recommends that models be used in a relative

sense due to their uncertainties and the differ ences that exist between model input data and design values applicable to determine atta inment. EPA directs that model results and other analysis be combined to establish a confirmed finding of attainment in a “weight of evidence” determination, particularly if the predicted future values are close to the standard. New approaches recommended by EPA guidance also require special processing of speciated data and a Specia ted Modeled Attainment Test (SMAT).

3.3.1 Model Choice

Annual meteorology has seasonal com ponents, reflected in EPA guidance recommending at least quarterly evaluation and analysis. Regional modeling is being performed for an entire year on a daily basis that can be processed to monthly or quarterly analysis as needed. Receptor modeli ng, with a speciated rollback approach used for the PM10 SIP with monthly meteorol ogical analyses and source identification combined into an annual composite, is bei ng updated for the PM2.5 analysis. Prior analysis determined that fall and winter seasons are most important for PM10 in the San Joaquin Valley and the winter remains the most important for PM2.5 due to increased carbon and nitrate particulates.

• Receptor Modeling Receptor modeling is performed by the District to establish a link between observed particulates and c ontributing emission sources using the combined outputs and techniques of several models. Receptor analysis of observed events and annual average particulate levels was performed by ARB in consultation with the District using the chemical mass balance (CMB) model. The output of this model is used in a receptor modeling s peciated rollback model developed by the

District to calculate the effect of predicted emission trends and adopted and proposed control measure reductions. The District developed receptor speciated rollback as one of its earliest improv ements to standard rollback modeling, with documented assumptions for the isolation of natural emissions and transport of emissions that would not be affected by the control program. The effort to remove sampling artifact and non-reactive spec ies has been incorporated into EPA SMAT

methods to correct similar issues for the regional m odeling. The District added a spatial area-of-influence element to more ac curately reflect the effect of controls on contributing sources. Re ceptor modeling methods us ed for the PM10 SIP have been revised to evaluate PM2.5 by modifyi ng assumptions to address fine particle mechanisms and with methodology revisions to reduce uncertainties for the PM2.5 annual standard. Further revision may occur to incorporate new findings of current regional modeling of secondar y particle formation.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-15 This receptor modeling met hod works well for analysis of di rectly emitted particles, but is less certain in predicting the effe ct of reductions of secondary precursors (gases that form particles in the air that may not produce particles in amounts directly proportional to the amount of emissions). The formation of secondary particulates has been examined with region al modeling to determine appropriate adjustments to predictions of secondary particulates. The receptor modeling approach uses direct (linear) assumptions for the connection of emissions changes to projected future contribut ions. This is adjusted to reflect the nonlinear chemistry

associated with nitrate formation as dete rmined by the regional model. Sulfate formation approaches linear rela tionship and is not adjusted for nonlinear chemistry in the receptor modeling. The expected result of linear projection is an overprediction of future concentra tion. The method anticipates uncertainty in the inputs and uses the over-prediction as a safety ma rgin for attainment modeling. The PM10 receptor modeling resulted in a sizable ma rgin of safety, projecting attainment several years after actual compliance wa s achieved. Comparing the results of PM2.5 receptor modeling with regional modeling resu lts and other pertinent information is important to develop a wei ght of evidence approach to determining

when attainment will be achieved.

• Regional Modeling EPA guidance expects regional modeling to play a larger role in

the PM2.5 modeled attainment test. The primary purpose of the regional modeling for the PM2.5 SIP is to provide an i ndependent analysis of t he reductions needed to achieve attainment. Regional photochemic al modeling has limitations for depicting the dispersion and removal processes that occur in scales finer than the grid resolution but provide equilibrium modeling fo r the most significant contributions to observed mass. Regional modeling uses the known emissions inventory in a bottom-up analysis that calculates the amou nt of mass that should be present due to the emissions. Using the model to predict mass from a future emissions inventory produces the best assessment of nitrate and sulfate levels that can be provided.

The use of the model results in relati onship to the design value provides a

reasonable estimate of future PM2. 5 nitrate and sulfate mass components.

Regional modeling of secondary particulat es has been conducted by ARB using

several different data sets and models. Results of regional modeling improve understanding of particle formation rates and ratios of precursors to particle formation, particularly for nitrate particu lates. These results have been used in conjunction with receptor modeling to enhance the accuracy and reliability of predicted effects of emission trends and adopted and proposed control measure reductions of secondary precursors. The first regional assessm ent used the Urban Airshed Model, modified to address aerosol chemistry (UAM-AERO). This assessment used the IMS-95 dataset (an ear ly component of CRPAQS) to evaluate a monitored event of nitrate particulate formation. Regional modeling was also

conducted for the later 2000- 2001 CRPAQS data, providi ng an update to the PM10 receptor modeling projections in 2006. A third round of region al modeling with the Community Multiscale Air Quality (CMAQ) model has been completed by ARB, hasSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-16 been used to develop SMAT projections fo r the SJV and is undergoing performance evaluation. If this provides a different regional photochemistry analysis for nitrate formation, the receptor modeling esti mates for nitrates will be reviewed.

3.3.2 Model Application

ARB is conducting regional modeling, positive matrix factorization ( PMF) evaluation for 2004 to 2006, and chemical mass balance (CMB) modeling for 2005 annual speciation

data for Fresno and Bakersfield. The Distric t is reevaluating prior receptor modeling (CMB and speciated rollback) for the pr ior PM10 plans (2000 annual evaluations), establishing PM2.5 speciation for these anal yses and projecting the concentrations from 2000 to 2005. The District has performed an analysis and receptor projection from 2005 to 2014 for the PM2.5 speciated versions of the 2000 annual evaluations the new 2005 PM2.5 CMB speciation for Fresno and Ba kersfield and the PMF evaluation. The receptor evaluations are relatively consist ent for all of these events providing a strong weight of evidence comparison. The regional modeling resu lts are not yet available.

Technical issues are being examined, and re vised calculations may be produced for the new CMB evaluations to improve profile se lection for improved model performance in the summer and for PMF regarding the handling and analysis of carbon artifact. Prior CMB profile selection was c onducted to match the winter dom inant sources. Improved profile selection is recommended to meet EPA recommendation for at least a quarterly evaluation of profile accuracy. Carbon arti fact handling in the PMF analysis should use
the most current and accurate CRPAQS findi ngs. Furthermore, ar tifact adjustments should follow EPA guidance and be included in relative mass comparison rather than be

excluded from calculations.

3.3.2.1 PM2.5 Speciation for Annual Rollback Modeling

The speciation data and CMB modeling result s for PM10 contain a combination of coarse and fine particles. The rela tionship between PM10 and PM2.5 is not proportional; therefor e special evaluation is requi red to develop an appropriate speciation set for PM2.5 rollback analysis fr om the CMB modeling per formed for PM10. To convert the PM10 annual CMB modeling and rollback analysis to PM2.5, the mass distribution must be replaced by PM2.5 speciation data or be calculated by other methods from the mass determined by PM 10 CMB modeling. The methodology includes the following co mponents and considerations:

• Fresno, Kern, Kings and Tulare count ies have 2005 PM2.5 design values that exceed the 15 microgram annual standard. Analysis is r equired for each of these

counties to determine emission reductions r equired to achieve compliance. PM2.5 speciation measurements are collected at Ba kersfield, Fresno, Modesto and Visalia. Fresno speciation data for PM2.5 covers t he period used for the rollback foundation annual PM10 CMB analysis (2000- 2001). Complete data for Bakersfield and Visalia is available for 2002 and thereafter, but is not available for 2000-2001. No PM2.5 speciation data was collected for Kings County; however, prior PM10 speciationSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-17 analysis and CMB modeling det ermined that Tulare and Kings County conditions are quite similar, allowing use of Tulare Count y speciation data with minor adjustments. The speciation data provides total mass fo r annual evaluation, nitrates, sulfates, geologic material and metals.

• Natural and regional background for PM2. 5 cannot be directly measured and is easily identifiable or separabl e from other measured local contributions. Background

concentrations have been established in the same manner used to establish background values for the PM10 rollback analysis. The significance of background

levels is that such material will not be affe cted by the District’s control efforts. Since rollback provides a linear projection of e ffect for reducing emi ssions, failure to exclude background will over-predict the effect of control efforts. All assumptions for background are now expressed as percentages of material. The background values for geologic material, nitrate and sulfate par ticulates have been set at 10% of the

observed concentration instead of a fix ed concentration. Dynamic background contributions of 10% were too high for use with PM10 due to high deposition rate and short average distance of travel; howev er, PM2.5 has greater travel distance and persistence in the atmosphere.

• Mobile exhaust and tire and brake wear were determined by CMB annual analysis

for PM10. From the em issions inventory we are able to establish that slightly over
90% of the mobile exhaust emissions ar e PM2.5 and approximately half of the tire

and brake wear material is PM2.5. The mass determined for PM10 rollback has been adjusted accordingly to establish a reasonable mass attribution for these

sources.

• Fresno annual rollback uses a design valu e derived from the annual speciation data set for the years 2000 and 2001. Fresno annual rollback uses limited elements of the annual PM10 CMB analysis, performed fo r the year 2000 with additional data from the first quarter of 2001, to provide mass estimates fo r motor vehicles and tire

and brake wear. The modeled contribution for motor vehicles and tire and brake wear has been adjusted by factors determin ed from the emissions inventory to be representative of PM2.5 material. The average of 2000 and 2001 PM2.5 speciation data is used to provide PM2.5 species for nitrates, sulfates, geologic material and unassigned (elements). Organic car bon and vegetative burning is composed organic and elemental carbon similar to th e motor vehicle emissions but contains both large and small particles. The ma ss for organic carbon and vegetative burning

has been calculated as the remainder of the annual PM2.5 speciated mass not assigned to the other categories.

• Bakersfield uses the same elements from the annual PM10 analysis but is required to use 2002 PM2.5 speciation data as the earlie st complete speciation available for this purpose. Modeling may be revised or adjusted in other ways if improvements to the methodology are identified by technical evaluation.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-18 • Visalia uses the same elements from t he annual PM10 analysis but is required to use 2002 PM2.5 speciation data as the earliest complete speciation available for this purpose. Modeling may be revi sed or adjusted in other wa ys if improvements to the methodology are identified by technical evaluation.

• Kings County uses Visalia speciation data for the year 2002 to establish PM2.5 mass with adjustment to motor vehicl e and tire and brake wear. The PM10 speciation data was very similar for Kings and Tulare counties in previous years, with the exception of fugitive PM10 emission s that are large parti cles. Motor vehicle

contributions were similar to Visalia in H anford but much less in Corcoran. Corcoran is the site that sets the design value for Kings County. Prio r CMB modeling of the

same event at both Visalia and Corcoran establishes an approximate ratio of the

motor vehicle and tire and brake wear contri butions at the two sites. Based on this evaluation, motor vehicle emissions and tire and brake wear are adjusted to 55% of

the Visalia concentration to reflect the sm aller urban contribution found in Corcoran.

• CMB results for Fresno and Kern provided by ARB were adjusted by 0.6 micrograms reassigned from organic carbon (OC) to unassigned mass as found with earlier CMB modeling. Inert material is common in SJV samples and the method of assigning all unaccounted mass to OC overestimates that profile.

3.3.2.2 PM2.5 Methodology Revi sions for Annual Receptor Modeling

• Cooking emissions, previously grouped wi th vegetative burning, are included in organic carbon associated with industr ial and commercial emissions.

• The speciated rollback analysis developed by the District provides spatial projection

of the area of influence of contributions. The PM10 methodology utilized different assumptions for contributions dominated by large particles and contributions dominated by fine particles, PM2.5 and sm aller. The PM10 travel distance assumptions for geologic and construction, tire and brake wear and unassigned mass utilized large particle assumptions wh ich are modified for the PM2.5 analysis

to be consistent with travel distance assu mptions for other contributions dominated by fine particles. Methodology for the def ined apportionment of mass to local and regional intrabasin transport has been adjusted from a fix ed ratio to a mass weighted calculation to improve accuracy and co rrelation to the conceptual model.

• For categories that are comprised of di rectly emitted particulates and secondary organic aerosol (SOA) formation of organi c carbon compounds a default split was used for earlier receptor modeling assuming an even split for the two pathways.
CRPAQS results indicate a maximum of secondary aerosol formation of fifteen percent of the observed ca rbon. The rollback analysis has been revised for this updated information. The emissions linka ge to SOA is ROG instead of TOG.

• Nitrate mass will be reevaluated to determi ne if any adjustments to linear projection are required. The 2003 analysis included nonlinearity adjustm ents obtained fromSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-19 analysis of UAM-AERO regional modeling of CRPAQS IMS- 95 data. The variation of nitrate chemistry is repr esented by the monthly variati ons of CMB modeling for the annual, which inherently incorporates the variation in nitrat e chemistry throughout the year. Regional modeli ng nitrate nonlinearity adjus tments are appropriate for episode evaluation but potentially in troduce a redundant penalty in the annual speciated rollback modeling. The linear projection of annualized rollback already

includes assessment of the variation of nitrate formation; therefore further adjustment with modeling response may c onstitute a redundant adjustment. The comparison of linear model estimation to the projections wit h regional modeling penalties for nonlinear nitrate response will be preserved until technical discussions on this matter are complete.

• Receptor modeling will use the alternate linear estimation assumptions for trapped

water. Water bonded to ammonium nitrate is approximated as equivalent to twelve percent of the mass and water bonded to amm onium sulfate is approximated as 26 percent of that mass. This method allows the water to remain incorporated in the proportional rollback because the trapped wate r is assumed to be proportional to the

ammonium nitrate and ammoni um sulfate mass. The li near assumption avoids the need to handle trapped water as a separate calculation.

3.3.3 Weight of Evidence

A weight of evidence approach compar es conceptual descriptions, episode categorization techniques, adjusted air qual ity trends, and other analysis to modeling results. The purpose of these additional analyses is to provi de additional insights into the projection of expected future air quality. The Speciated Modeled Attainment Test is the primary benchmark for quantif ying reduction targets to achieve attainment; however, supplemental evaluations may be appropriate if air quality tr ends or other information indicate that the targets will be met with less reduction than indicated or will require additional efforts to achieve compliance wit h the standards. The District has determined that the 15 microgram annual standard is more stringent fo r our air basin than the 1997 65 microgram daily standard. The new 35 microgram daily stand ard appears to be more stringent than the annual standard but is on a different timeline for planning and implementation and has not been used to dete rmine reduction goal s for this plan.

PM2.5 monitoring is a relatively new program; therefore, the historical record of data does not provide a sufficient history to ev aluate long-term trends and patterns. The

District and ARB will continue eval uation of data using a variety of statistical methods to identify potential key factors. Results of evaluations will be used to improve the District’s conceptual understanding of ev ents and may be considered to provide substantive data in the process of estab lishing a weight of evidence finding for

attainment.

The PM2.5 receptor modeli ng examines the 15 microgram per cubic meter annual

federal standard. When ev aluating the 50-microgram annual standard for PM10, anSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-20 uncertainty of one-microgram represented only a two percent variation; however, a onemicrogram uncertainty in the PM2.5 analysis represents a variat ion that is almost seven percent of the total allowed. This sets a very difficult bench mark for accuracy. Furthermore, PM2.5 is not a single material but a host of different materials with both separate behaviors and dependent interactions. Although there is a solid foundation of conceptual understanding, there are many technical is sues that remain open questions for continued study. The PM2.5 SIP will utilize all completed analyses available at this time; however, the District expects em erging technical information to enhance understanding of observed events to improv e our ability to predict future PM2.5

concentrations.

3.3.4 Speciated Modeled Attainment Test

EPA guidance acknowledges the difficulty in obtaining a data set for modeling that exactly matches the current design values and has developed a methodology to break down the modeling into the component consti tuents and use the model response in a relative sense to predict the reductions need ed to achieve attainment. This Speciated Modeled Attainment Test (SMAT) methodology is necessary because the different types

of materials come from differ ent types of sources and the em issions inventories of these sources vary at different rates and have diffe rent relationships for the contribution of PM2.5 mass. Therefore, the constituent ma terials that contribute to PM2.5 are not directly additive and must be calculated se parately and be added together as a final step to determine the total PM 2.5 mass. ARB will perform SM AT for the regional model and the District has developed an implementation of SMAT for the receptor modeling.

The Speciated Modeled Attainment Test (SMAT) methodology ca lculates remaining

mass other than the nitrates and water as or ganic carbon. This approach is too coarse

for use for the District. The bas is for this method is that most areas of the country do not have extensive control programs for geologi c material (fugitive dust) or extensive emissions from carbon sources subject to direct control (residential wood combustion and agricultural burning). Carbon particl e size growth and trapped carbon particles within nitrate and sulfate particulates that are not measured in the analysis methods are further losses not addressed by SMAT. CR PAQS modeling for particle size growth is under development but not available at this time . Metals are also not isolated by SMAT methods. For any elements not well-supported by the regional model results, receptor modeling or other substantive data will be reviewed to establish a weight of evidence finding for attainment.

Model response is used in a relative sense to predict the reductions needed to achieve attainment. Speciated Modeled Attainment Test (SMAT) calculations determine the amount of reductions needed from the major source categories to achieve compliance

with federal PM2.5 standar ds at all monitoring sites. Th e results of this process predict

future PM2.5 concentrations that would re sult from trends and current and proposed control programs. EPA guidanc e identifies how these calc ulations should be performed for a regional model. The District has deter mined applicability to the receptor analysis.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-21 The Speciated Modeled Attainment Test (SMAT) methodology is generally applicable throughout the country but conflic ts with certain important cons iderations critical to San Joaquin Valley Air Basin (SJVAB) assessment. Specific adjustments have been made to address technical issues specific to the SJVAB and to provide the most accurate

means to reflect the effects of emission reductions.

• The receptor analysis exceeds SMAT requirements by pr oviding extensive separation of contributing direct and secondary carbon sources. Secondary formation rate information developed by the CRPAQS program is used to quantify the secondary aerosol partition. By means of CMB model evaluation, carbon mass, along with associated trace metals and other c ontributions to the source signature, is

divided between:

o Motor vehicle emissions,

o Tire and brake wear,

o Stationary and area s ources carbon mass, and

o Vegetative burning.

• The receptor analysis exceeds SMAT requirements that recommend quarterly evaluation by performing monthly evaluati on and determining that CMB performance meets standards on a monthly basis. T he annual CMB modeling adjusts speciation selections for wood burning to reflect seasonal changes but otherwise uses a consistent set of speciation signatures. Pe rformance verification demonstrates that the selected profiles are acceptable for i dentifying and represent ing the contributing sources throughout the year. A further evaluation of CMB performance with quarterly optimized profiles will be per formed as a corroborative test.

• The receptor analysis exceeds SMAT requi rements by separati ng the contributions of geologic material from other sampling artifacts and unknowns. This is of particular importance to the SJ V due to the District regulations for control of fugitive

dust. The benefit of the Distr ict programs must be modeled separately from artifacts to quantify reductions appropriately.

• Receptor modeling addresses the SMAT requirement regarding trapped water in ammonium nitrates and sulfates using appr oved alternate linear assumptions. The linear assumption avoids the need to c onsider trapped water as a separate calculation. According to the linear a ssumption, water bonded to ammonium nitrate is approximated as equivalent to twelve per cent of the ammonium nitrate mass and is proportional to the amount of ammonium nitrate particulate mass present. Water bonded to ammonium sulfate is approximated as 26 percent of that mass and is proportional to the amount of ammonium su lfate particulate mass present. Because the amount of trapped water is established by the linear assumption method as proportional to the amount of the ammonium relat ed mass contributions, the speciated rollback analysis processes t he trapped water as an incorporated linear component of the ammonium nitrate and ammonium sulf ate particulate masses and does not establish a separate calculation column.

Technical note: The SMAT methodology separates out trapped water and ammonium, sulfate and nitrate ions. This is necessary in portions of the country that are dominated by sulfate emissions. Decreases in sulfate emissions canSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-22 actually cause increase in nitrate formati on in areas dominated by sulfates. The

associated water content of sulfates is much different than fo r nitrates and can require mass recalculation for areas wit h high sulfates. The SJVAB is dominated by ammonium nitrate particulates with lo w sulfate particulate concentrations; therefore this process is of minimal effe ct on the Valley PM2.5 mass calculation.

3.4 MODELING RESULTS

The modeling was conducted wit h an annual emission inventory PM 2.5 SIP Planning Projections - v1.00 RF#994.

Although ambient PM2.5 levels all sites in the Valley must be within the standard for the Valley to be redesignated into attainment, some sites already comply with the PM2.5 standards in force for this plan (annual st andard 15, daily standard 65). The revised daily standard of 35 has a separate timeline for planning and compliance.

A speciated modeled attainment test (S MAT) has been completed with receptor analysis modeling. The receptor modeling evaluation uses speciated rollback for its base calculations and is used in the pre scribed relative reduction method fro the Speciated Modeled Attainment Test. Vari ations from EPA methodology that use

additional information available for t he SJVAPCD and to adjust for assumptions documented by EPA and others as not appropria te for California are identified in the PM2.5 Modeling Protocol.

Table 3-2 San Joaquin Valley Ai r Pollution Control District PM2.5 Receptor Speciated Modeled Attainment Test

County 2005 Design

Value

(DV) ( μ g / m 3 ) Receptor

Modeled

SMAT RRF

2005-2014 Projected

Value 2014 (DV * RRF)

( μ g / m 3 ) Predicted Compliance Year San Joaquin 12.9 Meets Standard Meets Standard

Stanislaus 14.1 Meets Standard Meets Standard

Merced 14.7 Meets Standard Meets Standard

Madera - No data,

unclassified No data, unclassified
Fresno M1 17.2 .721 12.40 2010

Fresno M2 17.2 .753 12.94 2011

Fresno PMF 17.2 .707 12.17 2011

Kings M1 17.2 .770 13.25 2011

Tulare M1 18.2 .730 13.29 2013

Kern M1 18.9 .728 13.76 2014

Kern M2 18.9 .742 14.02 2014

Kern PMF 18.9 .746 14.09 2014San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-23 Method 1: 2000 baseline species were pr ojected to 2005 and then the 2005 projected species were used for projection to 2014. D ue to limited speciation data, Method1 will be used for Tulare and Kings.

Method 2: 2004-2006 species were pr ojected to 2014. This seco nd test is available for

Fresno and Kern.

PMF: A receptor projection was also pr epared from output of the PMF model for Bakersfield and Fresno speciated data.

A regional model evaluation has been prepared by ARB. Observations from 2000-2001 were used to prepare the model for performanc e evaluation. Relative response is established for emission inventory year s 2005 and 2014. Findings from a SMAT evaluation of the regional model shown in tabl e 3-3 compare very closely to the results of the receptor SMAT analysis shown in Ta ble 3-2. To maintain public records and archives for the PM2.5 SIP, the District has requested a copy of the SMAT calculation files developed by ARB for analysis of the r egional model output. However, due to the size (the previous version received by t he District was 54 megabytes) and technical nature of these files, the District does not intend to print or distribute these modeling analysis files.



### Table 3-3 San Joaquin Valley Air Pollution Control District PM2.5 Regional Speciated Modeled Attainment Test Reference and future year annual desi gn values for SJV FRM sites

determined from the regional model using EPA SMAT procedure
Site Code Speciation 2006 DV 2014 "Controlled" DV

Bakersfield - 5558 California BAC BAC 18.51 14.28

Bakersfield - 410 E Planz Road BEP BAC 18.86 14.70

Bakersfield - Golden State BGS BAC 18.64 14.39

Clovis - N Villa Avenue CLO FSF 16.39 12.72

Corcoran - Patterson Avenue COP VCS 17.24 13.27

Fresno - 1st Street FSF FSF 16.68 13.01

Fresno - Hamilton and Winery FSH FSF 17.16 13.47

Merced - 2334 M Street MRM M14 14.69 11.76

Modesto - 14th Street M14 M14 14.10 11.44

Stockton – Hazelton Street SOH M14 12.93 10.87

Visalia - N. Church Street VCS VCS 18.20 14.47

3.4.1 Discussi on of Results

• The four northern SJV count ies, San Joaquin, Stanislau s, Merced and Madera, need no additional reductions and already meet attainment requirements for the annual standard. Table 3-2 lists pr ojected values for 2014 becaus e all counties must meetSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-24 the standard to demonstrate attainment and anal ysis of Bakersfield does not support projection of attainment prior to 2014.

• Kings County – attainment is projec ted by 2011 with existing emission reduction commitments (Method 1 projection of 2000 PM2.5 species data to 2005 and projection from 2005 to 2011 for SMAT). The projected value in 2014 is 13.25

μ g/m 3 . Linear projection methods are cons ervative and, when used for the PM10 SIP, projected a later attainment date than was actually achieved.

• Fresno County attainment is projected by 2011 with existing emission reduction commitments. Linear projection methods are conservative and, when used for the PM10 SIP, projected a later attainm ent date than was actually achieved.

o Method 1 projects attainment by 2010 wit h no margin for error. Method 1 uses 2000 PM2.5 species data to 2005 and projection from 2005 to 2010 for SMAT projected a concentration of exactly fi fteen micrograms. T he projected value

in 2014 is 12.40 μ g/m 3

.

o Method 2 projects attainment by 2011 for Fresno. Method 2 analysis of 2004- 2006 speciation data, using essentially the same methodology as Method 1 with modification of secondary aeroso l evaluation due to use of a more restrictive motor vehicle emission prof ile. The projected value in 2014 is

12.94 μ g/m 3

.

o PMF evaluation projects attainment by 2011. Corroboration is available for Fresno County by PMF evaluation. T he PMF results were used to prepare a

SMAT evaluation. The PMF evaluat ion uses data from 2003 to 2006 for evaluation but excludes many samples t hat fail specified screening criteria. Therefore, the PM F data has gaps during the year and may not precisely

match an annual evaluation due to variati ons during the year that are not well represented. Despite the differences in assumptions and approach, the PMF

results correlate to Method 1 and Met hod 2 with a projected value in 2014 of

12.17 μ g/m 3 . The PMF results confirm and up date evaluation of regional transport by determining the contributi on of aged aerosol. This information has been used to update the assumptions fo r regional transport of nitrate and

sulfate for Method 1 and Method 2.

• Tulare County – attainment is projec ted by 2013 with existing emission reduction commitments (Method 1 projection of 2000 PM2.5 species data to 2005 and projection from 2005 to 2013 for SMAT). The projected value in 2014 is 13.29

μ g/m 3 . Linear projection methods are cons ervative and, when used for the PM10 SIP, projected a later attainment date than was actually achieved.

• Kern County attainment is projected by 2014 with emission reduction commitments. Linear projection methods are conserva tive and, when used for the PM10 SIP, projected a later attainment dat e than was actually achieved.

o Method 1 projects attainment by 2014. Method 1 uses 2000 PM2.5 species data to 2005 and projection from 2005 to 2014 for SMAT projected a

concentration of 13.76 μ g/m 3

.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-25 o Method 2 projects attainment by 2014. Method 2 analysis of 2004-2006 speciation data, using essentially the same methodology as Method 1 with modification of secondary aerosol evalua tion due to use of a more restrictive motor vehicle emission profile. T he projected value in 2014 is 14.02 μ g/m 3

.

o PMF evaluation projects attainment by 2014. Corroboration is available for Kern County by PMF evaluation. T he PMF results were used to prepare a

SMAT evaluation. The PMF evaluat ion uses data from 2003 to 2006 for evaluation but excludes many samples t hat fail specified screening criteria. Therefore, the PM F data has gaps during the y ear and may not precisely

match an annual evaluation due to variati ons during the year that are not well represented. Despite the differences in assumptions and approach, the PMF

results correlate to Method 1 and Method 2 with a projected value in 2014 of

14.09 μ g/m 3 . The PMF results confirm and up date evaluation of regional transport by determining the contributi on of aged aerosol. This information has been used to update the assumptions fo r regional transport of nitrate and

sulfate for Method 1 and Method 2.

Regional photochemical and parti cle modeling has also been completed by ARB. ARB confirms a finding of attainment for all monito ring sites in the District by 2014. Table 3.3 provides projections for the 2014 design value at all District sites that collect federal reference method (FRM) PM2.5 m onitoring data. The use of th is data is required for the implementation of the SMAT pr ocess that uses the design value established by this data with the relative change projected by the m odel to project the fu ture design value.

Extensive discussion of the regional modeling approach and doc umentation of results is in Appendix G to this plan.

It is important to note that both the recept or methods and regional modeling include all directly emitted and precursor reductions. Al l of these reductions have some effect on future particulate levels. Directly emitted PM2.5 reductions provide a direct benefit, while particulate precursors do not have t he same one-to-one relationship. SOx has a strong PM2.5 forming potentia l throughout the year. NOx has a strong particulate forming potential during winter months. ROG em issions have a very limited particulate contribution by formation of secondary organic aerosol. The technical issues regarding precursors have been extensivel y evaluated and are discussed in the modeling protocol (Appendix F) with sensitivity evaluations documented in the receptor analysis modeling

files.

Table 3-4 Regional Model Evaluation 2014 emissions without controls compar ed to 2014 emissions with controls

Percent of Reduction NOx PM2.5 SOx ROG

Defined State Measures (Strategy 4/26/07) 20 5 0 6

District Rules (Dft Plan 12/11/07) 4 8 4 0

Total Reduction 24 13 4 6San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-26 Receptor modeling includes t he reductions associated with a ll emission sources. The analysis provides separate correlation to PM2.5 contribution for geologic emissions, motor vehicle direct and secondary emissions , tire and brake wear particulate, organic carbon that is directly em itted or formed as secondar y organic aerosol, ammonium nitrate particulate that forms from NOx emissions, ammonium sulfate particulate that forms from SOx emissions, and vegetative burning emissions from residential wood burning, wildfires and agricultural burning.

An example of the relative contribution to the annual PM2.5 is shown in the following figure, which reveals that even after propos ed reductions in 2014, all of the categories continue to provide measurable contributions to the annual PM2.5 concentration. The

extensive contribution of amm onium nitrate from NOx rema ins dominant, but the other contributions are collectively half of the annual concentration.

Figure 3-4 Example annual PM2.5 sour ce contributions, Kern 2014, including

reductions

Receptor modeling results were evaluated by the District to determine the importance of reductions for particulates and precursors ot her than reductions of NOx (which reduce ammonium nitrate particulate). Each precur sor has a different relationship to directly emitted or secondary formation of particulate, ma king it difficult to describe reductions in common terms. The easiest approach to ident ify the importance of other reductionsSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-27 (PM2.5 direct or SO 2 ) with the receptor model is to remove the reductions from the analysis and determine how much more NOx reduction would be required to offset those reductions. The District analysis evaluated the highest concentration site analyzed by the receptor modeling (Kern County – Bakersfield California Street) for both

the 2005 to 2014 and 2009 to 2014 reductions. The re sult of this analysis is that without

the reductions of other PM2. 5 and precursors, an additional 172 tons of NOx reduction would be needed by 2014 to achieve the same improvement in PM2.5 as provided by

the other reductions. An additional 40 t ons would be needed for the more limited time period of 2009 to 2014. This demonstrates that the majority of other reductions (77% of the direct and other secondary reductions ) are being expeditiously implemented by

2009.

3.4.2 Weight of Evidence

A weight of evidence evaluation is required when the projected future year value is close to the standard. Projecti ons of the receptor evaluation predict that Bakersfield will have a design value close to the standard in 2014 and projections of the regional model predict both Visalia and Bakersfield as having future design values close to the standard in 2014. A weight of evidence determinati on that attainment will be achieved by the Plan is established by comparing the evidence provided by air monitoring data, technical analysis and the results of various m odels. The following is a brief weight of evidence evaluation by the District that dr aws upon the extensive weight of evidence documentation provided by ARB as Appendix H to this plan.

• Prior Accuracy of Receptor Ev aluation Methodology for PM10: Use of the speciated rollback receptor modeling for PM10 established the me rits of the method and demonstrated a strong correlation to obs erved improvement. As expected for a linear projection, the projected future va lues are conservative and attainment was achieved prior to the pr ojected date. Fourth quar ter fine particulate matter

dominates the annual PM10 ev aluations; therefore, mu ch of the PM10 annual

standard is also a PM2.5 annual evaluation. This establishes a strong probability that the receptor evalua tion will provide a reliable basis for PM2.5 modeling.

• Consistency of Method 1 Projection Methodology: The projection of 2000 to

2014 for the foundation data observations wa s essentially equal to the values predicted by projecting the 2000 data to 2005, resetting the species to the projected values for 2005, and projecting the change from 2005 to 2014. This indicates a stable relationship between the inventory and the concentration projections. An inconsistency in this result would hav e been unexpected and w ould have indicated greater uncertainty in the connection betwe en the observations and the inventory.

• Method1 and Method 2 Comparison: Method 1 and Method 2 provide receptor analysis based on different years of observa tions. The species data for the different year groups is quite different for carbon s ources; however, both evaluations reflect a similar response to emissions change for the period from 2005 to 2014, establishingSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-28 a consistent relative response factor ( RRF) for the speciated modeled attainment test (SMAT). The raw projected value fo r Fresno differs for the two evaluations, reflecting local changes in vegetative bur ning and possibly reduction of motor vehicle emissions, although motor vehicle emi ssion change is difficult to assess due

to the use of a different moto r vehicle emissions profile in the Method 2 evaluation. However, the relative reduction factor response for Fresno remains consistent for the two evaluations. Kern County evaluations project similar concentrations as well as a similar RRF value while reflecting di fferences in the attribution of carbon sources, at least in part due to the use of the different motor v ehicle profile for the Method 2 analysis. The relative consistency of 2005 episodes to 2000 episodes through relationship to the emissions in ventory indicates a strong proportional linkage between the receptor modeling PM2.5 concentration and the emissions inventory. The strong linkage between the invent ory and the observations

establishes a reliable foundation for usi ng the receptor mode ling to establish emission reduction targets to achieve attainment.

• PMF Confirmation of Regi onal Component Estimates: The PMF analysis provides an independent confirmation of r egional contributions previously estimated for Method 1 and Method 2. The PMF analysis also provides sufficient information to establish a receptor evaluation fo r corroboration with Method 1 and Method 2.

o The PMF results were used to revise estimation of nitrate and sulfate background contributions (particulate in flow from outside the District). The

PMF evaluation determines the contribut ion of “aged aerosol” by determining the amount of nitrates, sulfates and organic carbon that have reacted with

inflow of sea salt in the air. This reaction takes time to occur and establishes that the emissions are aged rather than fresh local emissions. The importance of identifying t he amount of inflow contri bution is that projected changes from District actions and trends in local emissions must be matched against the local source emissions and must not be reflected as affecting

contributions from outside the District . The accuracy of this evaluation prevents over-prediction of benefit from local actions.

o PMF results were used to prepare a receptor evaluation for corroborative comparison to the SMAT receptor ev aluations for Method 1 and Method 2. The PMF analysis uses data from 2003 to 2006 for evaluation, similar to the 2004 to 2006 period of data used for Met hod 2, but is required to exclude many samples that fail specified screeni ng criteria. Theref ore, the PMF data has gaps during the year and may not precisely match an annual evaluation due to variations during the year, if the variations ar e not well represented by the remaining data. Despite the differences in assumptions, input data processing and approach, the SMAT rec eptor analysis prepared with the PMF results correlates closely to Method 1 and Method 2 receptor evaluations. The RRF for the PMF receptor evaluatio ns vary from the other methods by two percent for Fresno County and less t han half a percent for Kern County. However, the attribution of contributi ng sources is quite different, with moreSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-29 mass attributed to nitrate and sulfate par ticulate and less mass attributed to vegetative burning particulate. The differences result in a dissimilar emissions response (9 percent difference for NOx reductions in Kern County).

o The processing of PMF for source i dentification conducted by ARB excluded a specified portion of the measured organic carbon mass due to collection with a non-federal reference method (FR M) sampler. Sampler comparison was conducted and the regression di fference between samplers was considered to be a sampler artifact of VOC incorrectly quantified as particulate matter. This methodology has been previously accepted as a

method for PMF to establish sources t hat correlate well to FRM samplers. The removed organic carbon mass was re stored to the receptor analysis
based on review of CRPAQS technical findings that establish a smaller estimate for the artifact and guida nce for SANDWICH (measured Sulfate, Adjusted Nitrate, Derived Water, Inferred Carbonaceous mass Hybrid Material Balance Approach) and SMAT data evaluation. With the removed organic carbon mass included in the rec eptor evaluation, the PMF 2003-2006 results for organic carbon match well with the Method 2 analysis of 2004- 2006 organic carbon. While some of the organic carbon is unquestionably sampler artifact from VOC, FRM sample rs also collect a smaller amount of such artifact. Per EPA guidance for SM AT, artifacts are retained in the analysis and compared proportionally. The receptor analysis methodology used by the District includes the or ganic carbon artifact with secondary organic aerosol (SOA - also formed from VOC) and projects future concentration based on changes in the VOC inventory. The proportional change is used in the SMAT evaluation and will reflect the comparable effect on FRM sampler mass that is also attributable to secondary organic aerosol and retained VOC quantified as particulate matter.

• Regional Modeling: Regional modeling performed by ARB also projects attainment by 2014. Regional model SM AT projections were compared by the District to findings provided by receptor modeling Methods 1, Method 2 and PMF. All sites were in very close agreement wit h the largest difference at Visalia. The peak value predicted by the regional model is 14.70 μ g/m 3 at Bakersfield Planz, a site not suitable for receptor evaluati on due to a lack of speciation data. The regional model prediction for Bake rsfield California site is14.28 μ g/m 3 which correlates well with the receptor Kern M2 prediction of 14.02 based on data from

the same site. The widest variation is at Visalia with a difference of 1.18 micrograms. Although the models dis agree on exact value for Visalia, both models predict a 2014 design value that complies with the annual standard.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-30 Table 3-5 Regional and Receptor Model Comparison

Site Code 2014 Regional 2014 Receptor Difference

Bakersfield - 5558 California BAC 14.28 14.02 0.26

Corcoran - Patterson Avenue COP 13.27 13.25 0.02

Fresno - 1st Street FSF 13.01 12.94 0.07

Visalia - N. Church Street VCS 14.47 13.29 1.18

• Model Reliability: A receptor model must demonstrate a reliable connection between the emission inventory and the obser ved concentrations. This test has been met for both the PM10 and PM2.5 recept or evaluations. Furthermore, the District has been using this approach long enough to determine that the method is reliable and conservative when estimating r eductions required to achieve attainment. The regional model is the third effort fo r regional photochemical modeling of the SJV performed by ARB. This approach uses state-of-the-science methods to model each day of a fourteen-month period. Performance anal ysis of the regional model

for submission to EPA as model documentat ion is still in progr ess; however, the correlation to receptor modeling gives a stro ng indication that the model will meet the required accuracy requirements.

• All Contributing Sources Considered: A review of contributing sources indicates that both the receptor and r egional modeling evaluations are comprehensive. The SMAT procedure of EPA guidance calls for evaluation of the major contributing sources. This procedure has been follo wed for the regional modeling and an equivalent process was established for the receptor evaluation. Both models use

the current emissions inv entory and common projections of reductions. Evaluation in the previous section identifies the im portance of including all key sources and reductions. Emission Inventories undergo c onstant review and improvement and the

California emission inventories are more comprehensive than other states due to inclusion of much smaller contributing sources.

• Air Monitoring Data and Trends: Analysis of recent air quality data and trends is included in Appendix H. Significant improvement has occurred from 2001 to 2006 in maximum concentration, frequency of hi gher concentration days and annual design value. Changes in chemical composition are strongly related to identified emission reductions in recent years providing c onfirmation and support for current modeling methods. Air monitoring data for 2007, whic h is not yet complete or certified, indicates that 2007 might reflect a one-year in crease in comparison to the last three years. Year-to-year variation is to be expected and is why design values are established over a three-year period. T he District performed a s ensitivity test with an estimated design value based on ava ilable uncertified data for 2007 and determined that the 2014 daily design value would still be far below the required 65 microgram standard. Evaluat ion of the top 25% of day s modeled by the regional model also indicate a projected future design value well below the daily standard while the annual projection is very close to the standard. The importance of theseSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-31 evaluations is the finding that attainment of the daily 65 microgram per cubic meter standard will be met by less reduction than is required to attain the annual standard. The annual standard is a more stringent requirem ent at this time and establishes the reduction goals for this PM2.5 Plan. Ho wever, the new 35-microgram standard is

more restrictive than the fifteen micr ogram annual standard and is expected to establish attainment goals when plans are developed and submitted for that

standard.

• Technical analysis: Technical issues are discussed in:

o Appendix F the SJV PM2. 5 SIP Modeling Protocol,

o Appendix E District Additions to the Conceptual Model

o Appendix H: Weight of Evidence

These issues are discussed extensively in the Appendices and briefly at the beginning of this Chapter. Evaluation of the technical issues does not contradict model projections, but provides insight into why the Valley has high particulate levels in comparison to other areas of the c ountry. The modeling approaches followed by the District and ARB incorpor ate and are consistent wit h our understanding of these

technical issues.

• Weight of Evidence Conclusion: Weight of Evidence eval uation conclude s that the model projections are consistent and proj ect attainment. The importance for the weight of evidence analysis of correla tion between modeling results that use different approaches and data is the finding that all of the modeling approaches are in agreement and project attainment by 2014. Both receptor and regional chemicalphotochemical evaluations arrive at the sa me conclusion and nearly identical values

for the sites comm on to both models.

Supplemental issues reviewed in the wei ght of evidence evaluation also provide support for the projection of attainment by 2014. A review of contributing sources indicates that both the receptor and regional modeling evaluations are comprehensive. Although there are fluctuations in the a nnual 24-hour data, it has

been determined that the annual st andard is more restrictive and that attainment of the daily 65 microgram per cubic mete r standard for this planning process will be met with less reduction than is required to attain the annual standard. Technical analysis has examined the conceptual model and identified additional considerations applicable to the SJV. The technical iss ues do not contradict model projections; rather they provide additiona l insight into why the Valley has high particulate levels in comparison to other areas of the country.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-32 3.4.3 Demonstration of Attainment

Attainment is demonstrated for each site that is projected to have future concentrations

at or below the federal standards. The predicted PM2.5 concentration may also be achieved with different equivalent reductions in individual sources or source categories. When the future predicted design value is cl ose to the standard, EPA recommends that a weight of evidence analysis be conducted to confirm the projection of attainment.

Required demonstrations:

• Attainment of the annual standard 15 μ g/m 3

• Attainment of the prior 24-hour standard 65 μ g/m 3

• Weight of evidence evaluation if ei ther projection is near the standard

• Evaluation of unmonitored areas (areas without monitoring sites)

Attainment of the annual standard is projec ted by 2014 by the regional photochemical model and all receptor evaluations. The pred icted value is within one microgram of the standard; therefore, a weight of evidence evaluation is appropriate. The predictions of these models are compared, along with air m onitoring data, trends and other technical information, to establish a weight of ev idence assurance that attainment will be achieved. The weight of evidence evaluat ion supports acceptanc e of the regional and receptor modeling predictions. Evaluation of the receptor mode ling identifies that attainment will not occur by 2009 with t he expected achievable reductions and will require the extensive NOx reductions propo sed by ARB for 2014. Reductions achieved by the District and current ARB efforts for a ll directly emitted and secondary particulate sources are important to achieving attain ment. The proposed NOx reductions for 2014

would not be sufficient to achieve attain ment without these ot her reductions. The strategy for attainment includes reduction of directly emitted PM 2.5 (geologic, mobile, organic carbon and vegetative burning) as we ll as reductions fr om SOx and NOx as precursors to ammonium sulfate and amm onium nitrate. Secondary organic aerosol particulate formation is also included in the modeling evaluation of motor vehicle and organic carbon contributions.

Attainment of the prior 24- hour 65 microgram standard is pr ojected to occur prior to 2014 and with much less reductions require d than are needed to attain the annual

standard. This mean s that the annual stan dard identifies the amount of reductions

needed to achieve attainment. ARB used the r egional model to evaluate the top 25% of days modeled to provide the annual analysis. Based on design values for 2005, ARB projected a 2014 value of 45 micr ograms or less at all sites. Due to concerns that the last two years have experienced slightly higher 24-hour values, the District also performed a screening assessment with estima ted design values for 2007 (based on incomplete and uncertified data). Evaluation by the District pr ojected a 2014 value of 53 micrograms. Both of these projections are well below the 65 microgram standard and do not require a weight of evidence evaluation.

Unmonitored area evaluation for the year 2014 was conducted by ARB and provides confirming evidence for the attainment demonstration. The unmonitored areaSan Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-33 evaluation requires examination of regional modeling results fo r the entire Valley. ARB has provided a screening assessment produced from the regional m odel results for the year 2014 to determine if any portion of t he modeling domain pred icts concentrations greater than the monitored locations. This initial analysis did not identify any grid squares that have higher values. ARB has committed to conduct further evaluation in accordance with EPA guidance should this be determined to be necessary; however, the screening assessment indicates that it is unlikely that any areas will be identified that require subsequent evaluat ion or temporary monitoring. The District and ARB will

confer with EPA to ensure that the unmonitored area evaluation provides sufficient

confirmation for the atta inment demonstration.

3.5 PM2.5 CONS IDERATIONS IN THE OZONE PLAN

In preparing the 2007 Ozone Plan , the control strategy wa s developed with utmost

consideration to future needs for the PM2.5 attainment plan. S ophisticated regional PM2.5 modeling for the San Joaquin Valley Air Basin using state of the science tools developed with data gathered from the $30 million field progra ms studying air pollution in the San Joaquin Valley was still under dev elopment at the time the ozone plan was completed and was therefore not available as a tool to es tablish a combined PM2.5 and 8-hr ozone plan. The District wanted some i ndication (order of magnitude estimates) of the Valley’s PM2.5 carrying capacity so that the District could gauge the effects of the Valley’s 8-hr ozone emission control strate gy on PM2.5 attainment. As a result, a simplified modeling exercise was conducted by ARB to help estimate the Valley’s carrying capacity for PM2.5. Evaluation of the San Joaquin Valley ozone control strategy to attain the federal 8-hr ozone standard determined that the ozone plan

include NOx emissions reductions that are close to what is needed for attainment of the 1997 PM2.5 standards by the maximum possible st atutory attainment date of April 5, 2015. Based on simplified modeling exerci ses performed at the time the ozone plan was completed, the ozone control strategy was determined to have a design that would provide most – if not all - of the reducti ons needed to attain t he PM2.5 annual standard.

3.6 PM2.5 EFFECT ON THE OZONE PLAN

Additional actions to achieve the PM2.5 standards by 2015 will accelerate compliance

with the ozone standard. The reductions of NOx that are valuable for PM2.5 compliance will support early compliance fo r the eight-hour oz one standard. Some reductions for the PM2.5 plan, such as geol ogic/soil material reductions, will have no material benefit for the ozone plan; however, no actions in the PM2.5 attainment plan

have been identified that would be detrimental to the oz one strategy. The smoke management programs enforced by the District throughout the year were initially developed to safeguard air quality during the ozone season and will continue to have that effect. The winter management of smoke and residential wood combustion has been enhanced to support the additional needs of the PM2.5 attainment strategy.San Joaquin Valley Unified Air Polluti on Control District April 30, 2008

Chapter 3: What is Needed to Demonstrate Attainment?

2008 PM2.5 Plan 3-34 This page intentionally blank.